.L2{
    display: inline;
}
.L1{
    display: inline;
}
#C1{
    display: block;
}
#C2{
    display: block;
}
.C1{

        border: 2px solid black; /* 2px 宽度，实线，黑色 */
        padding: 0; /* 内边距，让内容与边框有距离 */

        /*溢出后自动调节*/
        /*overflow: auto;*/
}
/*清除格式*/
/*#A1{*/
/*    clear: both;*/
/*}*/

.C1:after{
    content: "";
    display: block;
    clear: both;
}
.C2{
    float: right;
}
.C3{
    float: left;
}